Examples where a passenger-initiated emergency stop would help: The Eschede crash in Germany: https://en.m.wikipedia.org/wiki/Eschede_train_disaster https://en

Examples where a passenger-initiated emergency stop would help: The Eschede crash in Germany: https://en.m.wikipedia.org/wiki/Eschede_train_disaster https://en.m.wikipedia.org/wiki/Eschede_train_disaster -- part of the wheel came through the floor into the passenger compartment. The passenger couldn't find an emergency stop, and by the time they'd found a conductor and got their attention (which took minutes) the train crashed. Trap-and-drag accidents where somebody on the platform gets clothes trapped in the train door and is pulled along with the train as it starts to pull off. If you don't emergency-stop the train within seconds that person is likely to suffer serious injuries or die. Likely the conductor/guard isn't near that door and only passengers will have seen the problem.